/* vi: set sw=4 ts=4: */ /* Port to Busybox Copyright (C) 2006 Jesse Dutton <jessedutton@gmail.com> * * Licensed under GPL v2, see file LICENSE in this tarball for details. * * DHCP Relay for 'DHCPv4 Configuration of IPSec Tunnel Mode' support * Copyright (C) 2002 Mario Strasser <mast@gmx.net>, * Zuercher Hochschule Winterthur, * Netbeat AG * Upstream has GPL v2 or later */ #include "common.h" #include "dhcpd.h" #include "options.h" /* constants */ #define SELECT_TIMEOUT 5 /* select timeout in sec. */ #define MAX_LIFETIME 2*60 /* lifetime of an xid entry in sec. */ #define MAX_INTERFACES 9 /* This list holds information about clients. The xid_* functions manipulate this list. */ static struct xid_item { uint32_t xid; struct sockaddr_in ip; int client; time_t timestamp; struct xid_item *next; } dhcprelay_xid_list = {0, {0}, 0, 0, NULL}; static struct xid_item * xid_add(uint32_t xid, struct sockaddr_in *ip, int client) { struct xid_item *item; /* create new xid entry */ item = xmalloc(sizeof(struct xid_item)); /* add xid entry */ item->ip = *ip; item->xid = xid; item->client = client; item->timestamp = time(NULL); item->next = dhcprelay_xid_list.next; dhcprelay_xid_list.next = item; return item; } static void xid_expire(void) { struct xid_item *item = dhcprelay_xid_list.next; struct xid_item *last = &dhcprelay_xid_list; time_t current_time = time(NULL); while (item != NULL) { if ((current_time-item->timestamp) > MAX_LIFETIME) { last->next = item->next; free(item); item = last->next; } else { last = item; item = item->next; } } } static struct xid_item * xid_find(uint32_t xid) { struct xid_item *item = dhcprelay_xid_list.next; while (item != NULL) { if (item->xid == xid) { return item; } item = item->next; } return NULL; } static void xid_del(uint32_t xid) { struct xid_item *item = dhcprelay_xid_list.next; struct xid_item *last = &dhcprelay_xid_list; while (item != NULL) { if (item->xid == xid) { last->next = item->next; free(item); item = last->next; } else { last = item; item = item->next; } } } /** * get_dhcp_packet_type - gets the message type of a dhcp packet * p - pointer to the dhcp packet * returns the message type on success, -1 otherwise */ static int get_dhcp_packet_type(struct dhcpMessage *p) { uint8_t *op; /* it must be either a BOOTREQUEST or a BOOTREPLY */ if (p->op != BOOTREQUEST && p->op != BOOTREPLY) return -1; /* get message type option */ op = get_option(p, DHCP_MESSAGE_TYPE); if (op != NULL) return op[0]; return -1; } /** * signal_handler - handles signals ;-) * sig - sent signal */ static int dhcprelay_stopflag; static void dhcprelay_signal_handler(int sig) { dhcprelay_stopflag = 1; } /** * get_client_devices - parses the devices list * dev_list - comma separated list of devices * returns array */ static char ** get_client_devices(char *dev_list, int *client_number) { char *s, *list, **client_dev; int i, cn; /* copy list */ list = xstrdup(dev_list); if (list == NULL) return NULL; /* get number of items */ for (s = dev_list, cn = 1; *s; s++) if (*s == ',') cn++; client_dev = xzalloc(cn * sizeof(*client_dev)); /* parse list */ s = strtok(list, ","); i = 0; while (s != NULL) { client_dev[i++] = xstrdup(s); s = strtok(NULL, ","); } /* free copy and exit */ free(list); *client_number = cn; return client_dev; } /* Creates listen sockets (in fds) and returns the number allocated. */ static int init_sockets(char **client, int num_clients, char *server, int *fds, int *max_socket) { int i; /* talk to real server on bootps */ fds[0] = listen_socket(htonl(INADDR_ANY), 67, server); *max_socket = fds[0]; /* array starts at 1 since server is 0 */ num_clients++; for (i=1; i < num_clients; i++) { /* listen for clients on bootps */ fds[i] = listen_socket(htonl(INADDR_ANY), 67, client[i-1]); if (fds[i] > *max_socket) *max_socket = fds[i]; } return i; } /** * pass_on() - forwards dhcp packets from client to server * p - packet to send * client - number of the client */ static void pass_on(struct dhcpMessage *p, int packet_len, int client, int *fds, struct sockaddr_in *client_addr, struct sockaddr_in *server_addr) { int res, type; struct xid_item *item; /* check packet_type */ type = get_dhcp_packet_type(p); if (type != DHCPDISCOVER && type != DHCPREQUEST && type != DHCPDECLINE && type != DHCPRELEASE && type != DHCPINFORM ) { return; } /* create new xid entry */ item = xid_add(p->xid, client_addr, client); /* forward request to LAN (server) */ res = sendto(fds[0], p, packet_len, 0, (struct sockaddr*)server_addr, sizeof(struct sockaddr_in)); if (res != packet_len) { bb_perror_msg("pass_on"); return; } } /** * pass_back() - forwards dhcp packets from server to client * p - packet to send */ static void pass_back(struct dhcpMessage *p, int packet_len, int *fds) { int res, type; struct xid_item *item; /* check xid */ item = xid_find(p->xid); if (!item) { return; } /* check packet type */ type = get_dhcp_packet_type(p); if (type != DHCPOFFER && type != DHCPACK && type != DHCPNAK) { return; } if (item->ip.sin_addr.s_addr == htonl(INADDR_ANY)) item->ip.sin_addr.s_addr = htonl(INADDR_BROADCAST); if (item->client > MAX_INTERFACES) return; res = sendto(fds[item->client], p, packet_len, 0, (struct sockaddr*)(&item->ip), sizeof(item->ip)); if (res != packet_len) { bb_perror_msg("pass_back"); return; } /* remove xid entry */ xid_del(p->xid); } static void dhcprelay_loop(int *fds, int num_sockets, int max_socket, char **clients, struct sockaddr_in *server_addr, uint32_t gw_ip) { struct dhcpMessage dhcp_msg; fd_set rfds; size_t packlen; socklen_t addr_size; struct sockaddr_in client_addr; struct timeval tv; int i; while (!dhcprelay_stopflag) { FD_ZERO(&rfds); for (i = 0; i < num_sockets; i++) FD_SET(fds[i], &rfds); tv.tv_sec = SELECT_TIMEOUT; tv.tv_usec = 0; if (select(max_socket + 1, &rfds, NULL, NULL, &tv) > 0) { /* server */ if (FD_ISSET(fds[0], &rfds)) { packlen = udhcp_get_packet(&dhcp_msg, fds[0]); if (packlen > 0) { pass_back(&dhcp_msg, packlen, fds); } } for (i = 1; i < num_sockets; i++) { /* clients */ if (!FD_ISSET(fds[i], &rfds)) continue; addr_size = sizeof(struct sockaddr_in); packlen = recvfrom(fds[i], &dhcp_msg, sizeof(dhcp_msg), 0, (struct sockaddr *)(&client_addr), &addr_size); if (packlen <= 0) continue; if (read_interface(clients[i-1], NULL, &dhcp_msg.giaddr, NULL) < 0) dhcp_msg.giaddr = gw_ip; pass_on(&dhcp_msg, packlen, i, fds, &client_addr, server_addr); } } xid_expire(); } } int dhcprelay_main(int argc, char **argv); int dhcprelay_main(int argc, char **argv) { int i, num_sockets, max_socket, fds[MAX_INTERFACES]; uint32_t gw_ip; char **clients; struct sockaddr_in server_addr; server_addr.sin_family = AF_INET; server_addr.sin_port = htons(67); if (argc == 4) { if (!inet_aton(argv[3], &server_addr.sin_addr)) bb_perror_msg_and_die("didn't grok server"); } else if (argc == 3) { server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST); } else { bb_show_usage(); } clients = get_client_devices(argv[1], &num_sockets); if (!clients) return 0; signal(SIGTERM, dhcprelay_signal_handler); signal(SIGQUIT, dhcprelay_signal_handler); signal(SIGINT, dhcprelay_signal_handler); num_sockets = init_sockets(clients, num_sockets, argv[2], fds, &max_socket); if (read_interface(argv[2], NULL, &gw_ip, NULL) == -1) return 1; dhcprelay_loop(fds, num_sockets, max_socket, clients, &server_addr, gw_ip); if (ENABLE_FEATURE_CLEAN_UP) { for (i = 0; i < num_sockets; i++) { close(fds[i]); free(clients[i]); } } return 0; }